1. Field of the Invention
The present invention generally relates to portable electronic devices and more particularly to power conserving storage devices within portable computers such as magnetic hard disk drives.
2. Description of the Related Art
The use of direct access storage devices (DASD), such as magnetic disk drives, in portable computers has increased significantly over the past several years. Such computers typically have a portable battery pack that provides power to the various components of the computer when the computer is used away from a power outlet. It is important that the battery pack used to supply power to the portable computer be compact and lightweight. However, as the portable computers are increasingly used in locations where an external power source is unavailable, for example, traveling on an airplane, it is also increasingly important that the portable computers operate for significant periods of time between recharging of the battery pack.
The desire to achieve a compact and light weight design often competes with a desire for longer usage time of the computer between charging the battery pack. In order to increase operating time at the portable computer, various steps have been taken to reduce the power consumption of components used in the computer. For example, the central processing unit (CPU), often includes some form of power management function to reduce clock frequency of the CPU when the computer is in a power savings mode. In general, a power saving mode may be invoked to reduce use of power by a component of the computer when the component is not being used.
In the case of memory storage devices various power savings techniques have been employed. For example, in disk drives, the spindle motor uses a large percentage of the total power. In order to conserve power, it has been proposed that the spindle speed of the disk drive be reduced or stopped when the disk drive is not being used by the portable computer. In a typical approach, a normal operating spindle velocity is used by the disk drive during read and write operations to the disk. When the power saving mode is initiated, for example, when the disk drive is not accessed over a predetermined period of time, the spindle velocity of the disk is reduced or stopped to conserve power. When an access operation to the disk drive is initiated, the spindle speed is increased until the disk is rotated at the normal operating velocity prior to beginning the read or write operation. In other words, the power saving mode is disengaged prior to the commencement of read and write operations.
Similarly, low power hard disk drives are utilized in portable computers to extend battery life. Such low power hard disk drives commonly operate at relatively low rotational speeds (4200-4900 RPM) and reduced data transfer rates (120 Mb/s). To the contrary, a conventional desktop computer (AC powered), includes a hard disk drive which operates at higher rotation speeds (5400-7200 RPM) and increased data rates (195-225 Mb/s).
Therefore, the designers of portable computing devices must choose between performance and power consumption. If the designer chooses a fast hard disk drive for the portable computing device, the battery life will suffer if used away from an external power supply. To the contrary, if the designer chooses a slow drive to extend battery life, the performance of the device will suffer even if the computing device is connected to an external power supply. Therefore, there is a need to have a disk drive that behaves like a fast high-performance hard disk drive when the portable computer is connected to a external power supply, and behaves like a slow-speed low-performance disk drive, with reduced power consumption, when using the computer away from an external power supply, using its internal battery.
An example of a conventional power saving hard disk drive system is disclosed in U.S. Pat. No. 5,787,292, which is incorporated herein by reference. U.S. Pat. No. 5,787,292 discloses a multi-frequency zoned disk in which data is read and written from and to the disk at a reduced rotation speed in battery mode. The power savings obtained here are by the reduced power consumption of the motor running at a lower speed and by the reduced power consumption of the dominantly digital channel running at a lower data rate.
The object of the present invention is to provide a structure and method for reducing the power consumption of the hard disk drive even further than obtained with the previous art-methods as in U.S. Pat. No. 5,787,292, by also reducing the power consumption of the read/write electronics module, also referred to as the Arm Electronics (AE) module, of the hard disk drive when in battery mode.
A portable computer comprising a battery and a connection to an external power source; a two-speed data storage device being supplied power from one or more of the battery and the external power source; and a controller attached to the storage device, (wherein) the controller reduces a speed and data transfer rate of the storage device when the storage device is powered by the battery and increases the speed and data transfer rate of the storage device when the storage device is powered by the external power source.
The portable computer (wherein) the storage device includes at least one magnetic disk, (wherein) the controller reduces a rotational speed of the magnetic disk when the portable computer is powered by the battery and increases the rotational speed when the portable computer is powered by the external power supply, (wherein) the storage device includes a read/write electronics module, comprising a write driver circuit connected to a write head writing to the magnetic disk, (wherein) the write driver circuit includes a power supply having an output voltage supplied to the writehead, the output voltage being reduced when the storage device is powered by the battery and the output voltage being increased when the storage device is powered by the external power supply, (wherein) the power supply connected to the write driver circuit has multiple resistive elements, (wherein) the resistive elements determine the output voltage of the power supply, (wherein) the output voltage is reduced by disconnecting at least one of the resistive elements from the power supply and the output voltage is increased by connecting at least one of the resistive elements to the power supply, (wherein) a rise and fall time of a write current of the write head is increased by reducing the output voltage supplied to the write driver circuit and the rise and fall time of the write current is decreased by increasing the output voltage supplied to the write driver circuit, (wherein) the rise and fall time of the write current is changed inversely proportional to the rotational speed of the magnetic disk, (wherein) the storage device includes a read/write electronics module comprising a read amplifier connected to a (G)MR read head, reading magnetic transitions from the magnetic disk, (wherein) the read amplifier comprises multiple cascaded amplifier stages and, (wherein) tail currents of the amplifier stages are reduced when the storage device is powered by the battery and the tail currents of the amplifier stages are increased when the storage device is powered by the external power source, (wherein) the tail currents are changed proportional to the rotational speed of the magnetic disk.
A portable electronic device comprising a battery and a connection to an external power source; and a multi-speed data storage device being supplied power from one or more of the battery and the external power source, (wherein) a data transfer rate of the storage device is reduced when the storage device is powered by the battery and the data transfer rate of the storage device is increased when the storage device is powered by the external power source.
A method of conserving power in a portable electronic device comprising determining whether the electronic device is being supplied power from an internal battery or an external power source; reducing a data transfer rate of a storage device when the electronic device is powered by the battery; and increasing the data transfer rate of the storage device when the storage device is powered by the external power source.